dbObject: `order by` error "unknown column `d`", but column "id" was requested

[jeanmonet]

Fatal error: Uncaught Exception: Unknown column 'd' in 'order clause' query: SELECT * FROM last_obj ORDER BY d DESC LIMIT 1 in /MysqliDb.php:1996 Stack trace: #0 /MysqliDb.php(1584): MysqliDb->_prepareQuery() #1 /MysqliDb.php(734): MysqliDb->_buildQuery(1) #2 /MysqliDb.php(760): MysqliDb->get('last_obj', 1, '*') #3 /dbObject.php(360): MysqliDb->getOne('last_obj', NULL) #4 /dbObject.php(548)

The error was triggered by:

last_obj::orderBy("id", "desc")->getOne();

The error seems to appear from time to time: in two subsequent requests, one may fail, the other may succeed.

Any ideas on why this happens?